1. Field of the Invention
The present invention relates generally to antenna devices, and more particularly to a directional antenna device.
2. Description of the Related Art
In recent years and continuing, wireless communication technology using UWB (ultra-wide band) is attracting attention, as radar positioning is possible and communications of a large transmission capacity can be achieved. In 2002, the FCC (Federal Communication Commission) of the US authorized usage of a frequency band of 3.1 GHz through 10.6 GHz.
UWB is a communication method of communicating pulse signals in an ultra-wide band. Therefore, UWB requires an antenna having a structure with which signals can be transmitted and received in an ultra-wide band.
There is a proposed antenna including a bottom board and a power feeding body, to be used in the frequency band of at least 3.1 GHz through 10.6 GHz, authorized by the FCC (Non-patent literature 1).
Non-patent literature 1: An Omnidirectional and Low-VSWR Antenna for the FCC-Approved UWB Frequency Band, written and proposed by Takuya Taniguchi and Takehiko Kobayashi of Tokyo Denki University, at 2003 IEICE (The Institute of Electronics, Information and Communication Engineers) General Conference, B-1-133, on Mar. 22, 2003, at Tohoku University, Kawauchi Campus, classroom B201
However, this type of UWB antenna is nondirectional, and therefore, communication efficiencies are degraded when directivity is required.